1. Field of the Invention
The invention relates to a data transmission system for transmitting data between a rotating part and a stationary part, in particular between the rotating part and the stationary part of a computer tomograph, and also to a computer tomograph having a corresponding transmission system.
2. Description of the Relevant Art
With rotatable units such as radar installations or also computer tomographs, and also with linearly movable units such as crane and conveyor systems, it is necessary to transmit electrical signals or energy between units that are moveable relative to each other. For this, usually a conductor structure is provided in a first unit, and a suitable tap in a second unit. In the following explanations the term conductor structures relates to all conceivable forms of conductor structures which are suitable for conducting electrical signals. This also relates to known contacting slide paths or slip rings. Essential for transmission by means of rotary joints or linear “slide tracks” which also may be designed to be non-contacting is a small distance of transmission between the units that are rotatable relative to each other. Thus, a signal can be coupled-out optionally by means of a contacting connection, or without contact in the near field of a conductor structure.
From U.S. Pat. No. 6,433,631 B2 a device is known for data transmission in computer tomographs. A transmitted signal is applied to a strip line in a rotating part. On the stationary part a tap is provided which is guided along at a small distance of about 1 mm from the strip line. With computer tomographs the length of the strip lines is of an order of magnitude of about 5 meters. Thus, for data transmission rates of a few tens of gigabytes per second, signals must be conducted with a bandwidth of several gigahertz via a conductor system of about 5 meters length. This conductor system cannot be screened because it extends along a rotation gap. With increasing frequencies it becomes increasingly difficult to keep the radiation of high-frequency interference into free space below admissible limiting values.
In US 2004/0165652 it is suggested that the spectrum of the transmitted signals be modified. For this, special signals which are encoded with pseudo-random numbers are transmitted. Thereby the spectral power density of the signals is reduced.
In U.S. Pat. No. 6,862,299 B2 the use of clock regeneration circuits is suggested for improving signal quality from the optical data path.